Features:
+* make BlockIODeviceWeight=, BlockIODeviceBandwidth= runtime settable
+
+* split up BlockIOWeight= and BlockIODeviceWeight=
+
+* how to reset dynamically changed attributes sanely?
+
* when reloading configuration, apply new cgroup configuration
* implement system-wide DefaultCPUAccounting=1 switch (and similar for blockio, memory, fair scheduling?)